Aluminum alloys



' Patented Oct.31, 1933 ALUlVHNUM ALLOYS Robert T. Wood, Cleveland,Ohio, assignor to Aluminum Company of America, Pittsburgh, Pa., acorporation of Pennsylvania No Drawing. Original application September21, a 1932, Serial No. 634,155. Divided and this application November645,120

1 Claim.

This invention relates to aluminum base alloys containing magnesium. Theinvention has for its object the improvement of alloys of this class bythe addition thereto of about 0.05 to 2.0 per 5 cent by Weight ofcalcium. The invention is particularly concerned with the specificalloys hereinafter described.

The claim of this application covers certain matter divided from'mycopending application Serial No. 634,155 which is, in part, acontinuation of my copending application Serial No. 595,- 231.Inventions disclosed but not claimed herein are claimed in my copendingapplications Serial Nos. 595,231, filed February 25, 1932, 645,- 108 to645,119 inclusive, and 645,121 to 645,125 inclusive, all filed November30, 1932.

Considerable difilculty has heretofore been encountered in attempts tocommercially produce castings of aluminum base alloys containingsubstantial amounts of magnesium. This difficulty is encountered both inthe making of sand castings and permanent mold or chill-mold castings,although the nature of the difiiculty differs somewhat in each case. Inthe case of sand castings there occurs a reaction between the moltenaluminum base alloy containing magnesium and the ordinary sand-moldmaterials,

or vapors generated therefrom. There is also a reaction with theatmosphere. In addition, the magnesium-containing aluminum base alloydoes not flow freely through narrow mold sections at ordinary pouringtemperatures and, if the pouring temperature be raised, the solidifiedalloy is unsound. If the aluminum base alloy contain ing magnesium becast in a chill-mold the reaction effect is minimized to some extent,but the troubles'arising from cold-shuts and mis-runs are accentuatedbecause of the more rapid chilling of the molten metal. Theconsiderations 40 apply to the aluminum base alloys specificallydisclosed herein and particularly to such alloys.

I have discovered that when calcium is added to aluminum base alloys ofthe type and composition herein described, these difiiculties are, to aconsiderable extent, eliminated. The calcium should be present inamounts ranging from 0.05 per cent to 2.0 per cent by weight subject tospecific considerations as hereinafter disclosed.

In the melting of aluminum alloys of the compositions herein described,a viscous scum often forms at the surface of the molten metal. Failureof the molten metal to run properly through narrow mold apertures iscaused, in part, by shreds or particles of this scum being suspended inthe molten metal and oifering a resistance 30, 1932. Serial No.

to the free passage of the metal through the apertures. Regardless ofthe cause of this low fluidity, I have discovered that the addition tothe alloy of relatively small amounts of calcium,

in the preferred range between 0.05 to 0.5 per cent, improves thecasting characteristics to a very considerable extent and simultaneouslyeffects a reduction of the scum or dross collecting at or near thesurface. In the casting of articles in sand molds, I prefer to'addcalcium 5 in amounts less than about 0.5 per cent except in instanceswhere some reduction of tensile strength or other mechanical or tensileproperty is immaterial. In amounts of more than 0.5 per cent the calciumaddition produces the advantages enumerated herein but has a tendency tolower some of the physical properties of the alloys. This effect is notharmful when calcium is present in amounts of about 0.5 per cent orless, but when high strength is not a desideratum the calcium may beused in amounts up to about 2.0 per cent. In intricate permanent moldcastings, where casting troubles are very serious if no calcium beadded, the improved physical properties obtained coincident With theproduc- 30 tion of good castings more than offset the diminution inproperties which might otherwise result from the use of the calcium.

I have also discovered that when calcium is added to aluminum basealloys containing mag- 5 nesium, the amount of gas evolved duringsolidification of the alloys is considerably reduced. When from about0.05 per cent to 2.0 per cent by weight of calcium is added to thealloys, the amount of gas evolved becomes less marked with increasingcalcium content and the reduction of gas evolution may be so marked thatthe molten metal cools to the solidification temperature-with a smoothmirror-like surface. I prefer to restrict the amount of calcium added to2.0 per cent or less since above this amount the physical properties ofthe alloys may be too seriously affected. If the best physicalproperties are desired with an improved, although not complete, degreeof gas prevention, I keep the calcium content of the alloys between 0.05per cent and about 0.5 per cent.

In the application of the principles of my invention Ihave determinedthat certain aluminum base alloys containing magnesium are particularlybenefitted thereby. For example, a very useful aluminum base alloy isone containing about 2.0 to 9.0 per cent of magnesium and 0.05 per centto 2.0 per cent of calcium, as is also aluminum base alloy containingabout 2.0 t 11 least one of the class of metals here defined as antimonyand bismuth, such alloysbeing very useful where use at high temperaturesis contemplated. Calcium may likewise be added to improve such alloyswhen they contain, in addition to magnesium and antimony and/or bismuth, one or more of such alloying elements as cobalt, copper, nickel,manganese, zinc, etc. which may be added to modify or produce a specificproperty in the alloy.

The addition of 0.05 to 2.0 per cent of calcium is very beneficial inthe case of a series of 'aluminum base alloys which contain as majoralloying elements about 2.0 to 10.0 per cent of magnesium and about 0.2to 5.0 per cent of nickel. For instance, an aluminum base alloycontaining 3.0 to 7.5 per cent of magnesium and 0.2 to 2.0 per cent ofnickel is improved by the addition of 0.05

to 2.0 per cent of calcium as is, likewise, this same alloy when it alsocontains about 0.05 to 0.4 per cent of one or more of the class ofelements composed of antimony and bismuth. Another excellent aluminumbase alloy prepared in accordance with the principles of my' inventionis one containing 3.0 to 8.0 per cent of magnesium, 0.5 to 4.0 per centof nickel, 0.5 to 4.0 per cent of manganese, and. 0.05 to 2.0 per centof calcium, which alloy may also be improved, particularly forapplication at high temperatures, by the addition of 0.05 to 0,4 percent of at least one of the class of elements composed of annickel, 0.5to 3.5 per cent of chromium, and.

0.5 to 2.0 per cent of calcium has excellent casting properties and thehigh temperature properties of this alloycan be favorably affected bythe addition of 0.05 to 0.4 per cent of at least one of a class ofelements composed of bismuth magnesium, 0.5 to 5.0 per cent of nickel,1.0

to 6.0 per cent of copper, and 0.05 to 2.0 per cent of calcium with orwithout 0.05 to 0.4 per cent'of at least one of the class of elementscomposed of antimony and bismuth and with or without the furtheraddition of 0.5 to 3.5 per cent of at least one of a class of elementscomposed of cobalt and chromium, and with or without the furtheraddition of 0.1 to 1.0 per cent of at least one of a class of elementscomposed of tungsten, vanadium, molybdenum, titanium, and zirconium.

Other excellent alloys are those aluminum base alloys containing about2.0 to 10.0 per cent magnesium, 0.2 to 5.0 -per cent nickel, 0.1 to 3.5per cent cobalt, and 0.05 to 2.0 per cent of calcium. A particularexample of this class of alloys, which may also contain withconsiderable advantage 0.05 to 0.4 per cent of a class of elementscomposed of antimony and-bismuth, is the aluminum base alloy containing3.0 to 8.0 per cent magnesium, 0.5 to 4.0 per cent nickel, 0.1 to 3.0per cent cobalt, and-0.05 to 2.0 per cent calcium.

Among other magnesium-containing aluminum base alloys which I have foundto be particularly benefited by the presence of calcium are numbered thealuminum base alloys containing 3.0 to 8.0 per cent of magnesium, 1.0 to6.0 per cent of copper, 0.5 to 3.5 per cent of chromium, and 0.05 to 2.0per cent of calcium, with or without the addition of 0.05 to 0.4 percent of at least one of a class of metals composed of antimony andbismuth and with or without the addition of other alloying elements.

The alloys herein described may be produced by the usual methods ofalloying metals. The calcium is preferably added to the molten alloy bythrusting the calcium beneath the surface with tongs or other suitableinstrument. The

aluminum used in preparing the alloys may be pure orit may contain theimpurities found in commercial grades of this metal. Ordinarily a goodcommercial grade of virgin aluminum willgive excellent results and ispreferable.

Having thus explained and described my invention, Iclaim:

A metallic alloy consisting of 3.0 to 8.0 per cent by weight ofmagnesium, 0.5 to 3.5 per cent by weight of chromium, 1.0 to 6.0 percent by weight of copper and 0.05 to 2.0 per cent by weight of calcium,the balance being aluminum.

- ROBERT T. WOOD.

